1. Field of the Invention
The invention relates to a brake actuating device with a means for readjusting a brake, in particular a vehicle brake, where a brake lever is furnished, which brake lever performs together with a brake shaft a pivoting motion around a rotation axis of the brake shaft, which pivoting motion results in an actuation of a brake in the sense of an overcoming of a brake release gap for the purpose of engaging a brake lining contacting two brake drums.
2. Brief Description of the Background of the Invention Including Prior Art
A device of the kind recited above is known from the German Patent DE-PS 1,480,038. The known device includes a slack readjustment device, which allows to adjust the position parts of a brake actuator relative to each other, namely adjusting the position of a brake linkage rod and of a brake lever disposed on the brake shaft. The adjustment serves to provide a continuous readjustment of the position of the parts of the brake actuator in the sense of a maintaining of a preset brake release gap. This readjustment is performed to assure a uniform response behavior of the brakes or, respectively, a uniform brake behavior which, last but not least, is subject matter of corresponding legal and/or regulatory requirements regarding driving safety.
Wear or defects of the slack readjustment device and of its actuating mechanism can, however, effect a deficient readjustment with the consequence that the brake release gap, predefined by the brake type, can no longer be maintained in the course of the driving operation and then does no longer correspond to the actual brake lining wear. A defective readjustment or a complete lack of a readjustment is recognizable in the recited device only by a changing brake actuating stroke, by a decrease in the braking effect, or by a failing of the braking effect. However, this undesired change of the brake release gap occurs only gradually and usually over a longer period of time and is therefore initially hardly perceivable. Therefore, there exists a need to give the operator the certainty with regard to the actual state of the brake release gap and/or the wear of the brake lining for safety reasons.
The German Patent DE-PS 2,427,049 to Kurt Oelsch teaches an electrical distance regulator. A contact pin is guided along a straight line, a common casing is furnished for the contact pin and for an input member. The input member is led in a straight direction perpendicular to the contact pin and the input member with the inclined face forms an easily exchangeable component group in the casing. This reference shows operation of a regulator pin.
The German Patent Application Laid Out DE-OS 2,520,851 to Peter Lehner teaches a device with a regulator member for capturing the effect of a moving element on a scanning system. A contact pin of the capturing system is disposed slidable perpendicular to the direction of motion of a wedge-shaped element for changing of the switching duration. This reference shows that the regulator member can be used to change the switching time.
The German Patent Application Laid Out DE-AS 1,258,445 to Anton Hohner teaches a device for the monitoring of the brake position and of the wear state of the brake shoes at disc brakes of rail vehicles, where the disc brakes act together with automatic brake actuation regulators. The brake actuation regulators, connected to the brake piston, and the brake actuator are in each case connected with indicator shafts, disposed perpendicular to the vehicle longitudinal axis in a horizontal direction for the transformation of the axial motion into a rotation motion. Indicators are disposed at ends of the indicator shafts, protruding on the two vehicle sides via bogie or truck side rails in front of scales. This reference shows that the brake condition can be displayed on a scale.
The German Patent Document DE-OS 2,318,331 to Fritz Nigg et al. teaches an electronic scanning device with levers. A second lever of a switching mechanism can be disposed pivotable on the first lever of the mechanism and the motions of the movable element are controlled by a transducer. This second lever is subject to the effect of an elastic element and of two stop means, such that the first stop means is in an operating connection with the two levers and acts against the force of the elastic element. The reference teaches that the pivoting motion of the second lever can be limited versus the first lever in the direction of the elastic element, if the first lever is pivoted opposite to the force of the elastic element. This reference shows that lever actions can be electronically captured.
The German Printed Patent Publication DE-OS 3,738,294 to Jochen Hahne et al. teaches a safety device for an automatic slack adjuster upon malfunctioning of same in a brake actuator of rail vehicles. After a certain level of force has been surpassed, a support device allows a spatial change of the control stop, whereby a signal indicator, connected to the control stop, transfers these changes of the starting position to a display. The reference teaches that changes relative to a starting position are shown on a display.
The German Petit Patent Application 6,752,413 to Willi Scholz teaches a slack adjuster. The adjuster is equipped with an only rotary supported readjustment means, i.e. a collar, a readjustment wheel, preferably a readjustment rotary disc, which readjustment means is furnished with recesses or protrusions, respectively, serving as counter support, and distributed along an imaginary subdivision circle. The reference teaches a readjustment of slack adjusters relative to a previously maintained position.
The German Printed Patent Document DE-OS 1,455,913 to Leo Goldman et al. teaches a device for the display of the wear of brake linings. The reference teaches a rotary mounted cam shaft, which carries a cam disposed between spreadable brake shoes. The brake shoes are furnished with brake linings. The brake linings can come to a rest position at a drum. An adjustment lever, adjustable in a rotary manner, is connected to the cam shaft. The reference teaches an adjustment of a brake shoe relative to a brake lining.
The German Democratic Republic Patent DD-PS 274,087 to Torsten Schmandke teaches a device for generating digital signals, which reflect tolerance deviations of rotating or linearly moving bodies. The reference teaches that the deviations from a set position of a mechanical element can be represented by digital signals.
The German Printed Patent Document Laid Open DE-OS 3,713,562 to Eckehard Schmitz teaches a method for determining the position of adjustment elements with inductive direction indicators.
The German Printed Patent Document Laid Open DE-OS 3,242,537 to Roland Schempp teaches an electromagnetic adjustment device.
The German Printed Patent Document Laid Open DE-OS 3,010,498 to Peter Liermann et al. teaches a device for measuring the brake lining wear.
A brake lever with an automatic readjustment of the brake operating shaft, is known from the European Patent Document EP 0,030,766 A1. The reference EP 0,030,766 A1 teaches the drive of the slack readjustment device to be furnished by a gear wheel, by a worm connected fixed against rotation to the gear wheel, and by a worm wheel drivable by a worm, instead of the gear rack and the pinion of the present invention. The drive of the slack readjustment device is also always moved between end stops of a most motion device in two direction during a brake lever turn.
In case of a defect or deficiency of the above-recited and described slack readjustment device, i.e. if the wear of the brake elements, caused by the driving operation, is not compensated by an adjustment of the brake operating shaft relative to the brake lever, then a brake lever turn occurs during brake actuation which surpasses the final position.
A device for the display of the brake lining wear of heavy road vehicles such as, for example, trucks, buses, pulling machines or the like is taught in the German Printed Patent Publication DE-OS 2,248,927 to Helmut Hase. The reference teaches to employ a switch 19, actuated by contact pin 15, which is connected to display member.